A rotor is a rotating component of a turbine or a generator. The reliability of a rotor is a major concern to turbine operators such as electric utilities. In order to promote operational safety and prevent potential failures, nondestructive examinations (“NDEs”) are regularly performed to inspect the integrity of rotors and estimate the state of system integrity. A type of NDE includes the use of ultrasound techniques to detect flaws or defects in a rotor.
In an ultrasonic inspection, indications of any flaws or defects such as material discontinuities are detected through the use of ultrasound probes and are reported as digital information. The digital information is then evaluated to determine the size and shape of the flaws or defects. Performing the evaluation is not a trivial task and involves engineering know-how as well as experience. However, even with this know-how and experience, the evaluation is a time consuming process. In addition, many assumptions are made and safety factors are added to make a representative assessment of rotor integrity. As a result, many ultrasonic inspection systems are highly conservative with respect to data analysis in order to reduce risks. This results in inaccurate flaw size estimation and life prediction. In recent years, equipment life extension has become an important maintenance service aspect since a large number of rotors in electric utilities are close to reaching the limit of their original design life. Due to the substantial cost of replacing a rotor, it is desirable to extend the operating life of a rotor. In order to reliably predict a safe operating life of a rotor, the location and size of a flaw or defect needs to be estimated with high degree of accuracy. Accordingly, a more accurate and user friendly method for ultrasonic inspection of rotors is desirable.